Doctors in America have warned that a cinnamon-eating craze popular with teenagers is potentially harmful.

The "Cinnamon Challenge" involves trying to swallow one teaspoon of cinnamon without water, often while being filmed.

Numerous videos of teenagers attempting the prank have been posted on YouTube.

But a report published in the May issue of the Pediatrics journal said 30 American youngsters had required medical treatment after ingesting the spice last year.

Cinnamon, which is made from tree bark, is a caustic substance that can cause scarring in the lungs, the report said.

Other symptoms can include choking, throat irritation, respiratory trouble and collapsed lungs.

There is no suggestion eating cinnamon in small quantities is harmful.

Dr Stephen Pont, a spokesman for the American Academy of Pediatrics, said the report was "a call to arms to parents and doctors to be aware of things like the Cinnamon Challenge".

Dejah Reed, 16, who spent four days in hospital after attempting the Cinnamon Challenge and now suffers from shortness of breath, said: "I was laughing very hard and I coughed it out and I inhaled it into my lungs. I couldn't breathe".

She added she had read about the challenge on Facebook and thought it would be "cool" to attempt it.